The invention relates to a method of and to an apparatus for building a continuous stream of fibrous material, such as fragments of tobacco leaves, filter material for the making of filter mouthpieces, artificial tobacco, reconstituted tobacco and the like. More particularly, the invention relates to improvements in a method of and in an apparatus for making a stream which contains a surplus or excess of fibrous material and from which the surplus must be removed in order to leave a rod-like filler which is ready to be draped into a web of cigarette paper, artificial cork or other suitable wrapping material.
The following description will deal with the making of a stream of tobacco in a cigarette rod making machine with the understanding, however, that the same method and the same apparatus can be used with equal or with similar advantage for the making of a stream which can be converted into a cigarillo rod, a cigar rod or a filter rod.
The making of cigarettes involves withdrawal of comminuted tobacco leaves from a source of supply in a distributor (also called hopper) and conversion of the withdrawn tobacco into a continuous stream which contains a surplus. The surplus is removed by a so-called trimming or equalizing device which severs the fibers projecting beyond a predetermined (trimming) plane so that the trimmed or equalized stream constitutes a rod-like filler which is ready for draping into cigarette paper or the like. The surplus must be reused since tobacco constitutes the most expensive constituent of cigarettes. As a rule, or in many instances, tobacco particles which are withdrawn from the source of supply are converted into a shower whose particles are caused to deposit at one side of an endless foraminous belt conveyor to form a continuous stream which advances past the cutter or cutters of the means for removing the surplus. It is also customary to singularize or loosen the particles of tobacco which are withdrawn from the source of supply in order to facilitate the making of a continuous stream wherein each successive increment contains the same or substantially the same quantity of fibrous material. The shower can be formed mechanically or pneumatically, and the shower can be advanced toward the respective side of the belt conveyor by mechanical and/or pneumatic means. The surplus which is removed at the trimming station can be returned into the distributor and admitted to fresh tobacco particles in a number of different ways.
For example, the returned surplus can be admitted into the supply of fresh tobacco particles so that it is caused to pass again through the withdrawing unit and to undergo a singularizing or loosening treatment. Such singularizing or loosening treatment invariably or nearly invariably involves at least some undesirable comminution of tobacco shreds.
In accordance with another prior proposal which is discussed, for example, in U.S. Pat. Nos. 3,244,184 and 3,045,681, surplus tobacco is admitted to one side of the shower of fresh tobacco which is on its way toward the admitted surplus tobacco occupies a predetermined portion of the trimmed stream (filler).
British Pat. No. 976,145 discloses means for delivering surplus tobacco into a predetermined region of the stream building conveyor. The proposal which is discussed in the British patent and the proposals which are discussed in the aforementioned U.S. patents exhibit the drawback that the surplus is not uniformly distributed in the filler downstream of the trimming station.
U.S. Pat. No. 3,732,871 discloses a distributor which is provided with means for accumulating so-called tobacco shorts at a predetermined location and for admitting shorts into the shower of fresh tobacco in such a way that the shorts accumulate in a predetermined portion of the tobacco filler. This proposal exhibits the same drawbacks as the proposals in the previously discussed patents.